Lost too many troops

I used 2 attack waves of to attack a bandit leader camp of 200. I lost both attacking units while the enemy camp lost only 15 guard dogs. My units attacked about 15 seconds apart. Why wasn't the damage on the enemy units cumulative from my two attacking camps?

Wounded bandits fully recover between waves. Only the dead stay dead.
what are the bandits you are trying to beat?

Remember guard dogs also have first strike.